Mobile x-ray apparatus are of particular value in intensive care unit (ICU) and other environments where timely acquisition of a radiographic image is important. Because it can be wheeled around the ICU or other area and brought directly to the patient's bedside, a mobile x-ray apparatus allows an attending physician or clinician to have recent information on the condition of a patient and helps to reduce the risks entailed in moving patients to stationary equipment in the radiological facility.
As mobile x-ray systems have become more widely accepted and used, continued research and development has expanded their capabilities beyond those of single-image radiography, based on the x-ray film radiography model. By configuring mobile x-ray systems with an array of multiple, smaller x-ray sources, such as sources formed using carbon nanotube (CNT) technology, additional imaging modalities can be provided. This allows the mobile x-ray apparatus to provide not only conventional 2-D x-ray radiography images, but also to provide volume imaging using tomosynthesis or computed tomography (CT) methods, such as cone-beam computed tomography (CBCT), as well as fluoroscopy using multiple x-ray sources. To provide this expanded capability, the x-ray source can have a single x-ray emitter tube of conventional design, supplemented by multiple x-ray emitters, including an array of carbon nanotube (CNT) x-ray sources, for example.
In order to allow multiple modalities and maintain system portability, operational parameters such as positioning of the x-ray source(s) relative to the patient, dosage levels, operator procedure, and other factors must be readily changeable. This places some demanding requirements on design of support and positioning hardware for the x-ray head, requiring various guidance and guard elements that do not interfere with portability and smooth operation.
One concern for mobile x-ray equipment relates to maintaining sufficient distance between the x-ray source and the patient. If the patient is too close to the x-ray source, radiation levels can be excessive and image quality can be poor. International Electrotechnical Commission (IEC) standard IEC 60601-1 presents a number of general requirements for safety for medical electrical equipment. Among stipulations for compliance with IEC 60601-1, is the requirement for a physical barrier that is no less than about 30 cm from the x-ray source. This physical barrier forces the distance between the patient and the source to exceed at least about 30 cm for any of the imaging modalities available from the mobile x-ray system.
Thus, it can be appreciated that there are a number of considerations related to proper patient care, x-ray source positioning, and operational procedures for a mobile x-ray apparatus that provides multiple imaging modalities.